1. Field of the Invention
The invention relates to a running gear unit for low-floor rail vehicles including a running gear frame on which individual wheels are rotatably mounted through a respective rocker, the rocker is articulatingly attached and supported by primary springs, the running gear frame is connected to a car or carriage body of the low-floor rail vehicle through two articulated rods which are articulatingly mounted at one end at a distance from one another on a crossmember of the running gear frame and at the other end are likewise articulatingly attached to the car or carriage body, the car or carriage body of the low-floor rail vehicle is supported on the running gear frame through secondary springs which are mounted near the transverse ends on the crossmember, and transverse stops disposed at a distance from one another in the crossmember limit the transverse movement of the car or carriage body relative to the running gear unit.
Published European Application No. 0 384 512 discloses a running gear unit in which the frame of the running gear unit is constructed approximately in the shape of an H with a double crossmember. The double crossmembers are connected to one another at their transverse ends by outer longitudinal members which project slightly beyond the double crossmembers in the longitudinal direction of the running gear unit. Disposed between the double crossmembers is a transverse bolster beam which can be moved vertically and horizontally in the transverse direction. This transverse bolster beam is suspended at its transverse ends, through suspension rods, in secondary springs which are supported on outer longitudinal members of the running gear unit. In the center, the transverse bolster beam bears a receptacle for a pivot pin of the car or carriage body. Abutments, through which the car or carriage body is supported during cornering, are provided on the transverse bolster beam in the transverse direction of the running gear unit, on both sides of the receptacle for the pivot pin.
Near their longitudinal ends, the outer longitudinal members of the running gear frame carry individual wheels on rockers, the rockers are articulatingly attached to the outer longitudinal members and the rockers are supported relative to one another and on the running gear frame through primary springs.
The disadvantage of the above-mentioned structure is the configuration of a transverse bolster beam and its suspension on the secondary springs, which on one hand represents a complex construction and on the other hand requires such a great overall height in the region between the individual wheels of one longitudinal side of the running gear unit that the low-floor construction of the low-floor rail vehicle is compromised to a considerable extent, at least in that region, and it is not possible to use transverse seats. A further disadvantage of the already known construction resides in the fact that due to the guidance of the running gear unit on the car or carriage body by means of a pivot pin, additional hunting or side motion dampers are required for use in low-floor rail vehicles and they reduce the cost-effectiveness of the running gear unit.
Running gear units with individual wheels are furthermore known from Published European Application No. 0 129 772. In the case of that running gear unit, the individual wheels are likewise mounted on the frame of the running gear unit through rockers. However, the running gear unit in that prior publication is so tall in the region between the wheels of one longitudinal side of the running gear unit that it cannot be used for low-floor rail vehicles with a continuous car or carriage floor.
Individual wheels for running gear units for use in underground rail vehicles are furthermore known per se from German Published, Non-Prosecuted Application DE 35 38 513 A1. In that prior publication, the individual wheels are suspended on the car or carriage body through rockers.
Also known in practice are rockers for the articulated attachment of wheel axles for rail transport where the rockers are supported on the bogey or truck frame through springs.